Based primarily on in vitro studies, laminin alpha1 is believed to play important roles in early lung development, yet it is not expressed in normal adult mouse or human lung. However, we recently detected laminin alpha1 expression in adult mouse lungs following bleomycin-induced lung injury. SPECIFIC AIM 1 of this proposal is to define in vivo roles for laminin alpha1 in lung development and repair. Conventional laminin alpha1 knockout mice die at E5, prior to lung bud formation. Therefore, we will develop conditional laminin alpha1 knockout mice. With these mice and a doxycycline-inducible cre/lox system, we can obtain temporal-spatial control of laminin alpha1 expression. We will use this system to regulate laminin alpha1 expression at various stages of lung development and during bleomycin-induced lung injury. These studies will determine how the absence of laminin alpha1 affects lung development and repair. To elucidate the mechanisms by which laminins play roles in alveolar re-epithelialization following diffuse alveolar damage, SPECIFIC AIM 2 will focus on the roles of laminins-1 and -10 in epithelial cell proliferation, migration, and differentiation. Better understanding of the role of BM components like laminins in lung development and repair will enhance the ability to promote restoration of lung structure and function after diffuse alveolar damage.